There has been a considerable desire to utilize materials for delineating traffic lanes on highways and the like which would retroreflect light rays impinging thereon so as to provide maximum visibility. To this end glass retroreflective beads have been incorporated in coating materials utilized to paint line delineating markings and plastic strips having retroreflective properties have also been employed. There has also been a significant amount of efforts to utilize retroreflective cannisters and other structures which would project above the surface of the roadway, all of which have proven useful but limited in their degree of acceptance.
One of the major criteria for such roadway materials is that the upper surface thereof be able to withstand the considerable abrasion and impact that occurs during use. Embedding the materials in the surface of the roadway tends to reduce their effectivenss since the light rays impinging thereon from the headlights will in large measure be at an angle to the roadway surface of about 1 to 15.degree.. As a result, retroreflective formations disposed at the level of the top surface or therebelow will generally be inefficient since the angle of incidence is so small relative to the plane of the retroreflector strip.
Minnesota Mining and Manufacturing Company has long sold material under the trademark SCOTCHLITE which relies upon minute glass spheres embedded in a matrix of synthetic resin to provide such retroreflection and materials of this type have been used as highway type markers as well as in signs and other applications. Molded cube corner retroreflectors have long been known as evidenced by Straubel U.S. Pat. No. 835,648 granted Nov. 13, 1906; Hedgewick et al U.S. Pat. No. 3,258,840 granted July 5, 1966; and Jungersen U.S. Pat. Nos. 2,310,790 granted Feb. 9, 1943 and No. 2,444,533 granted July 6, 1948.
Recently it has been proposed to manufacture retroreflective materials employing minute cube corner formations cast upon one surface of a preformed body member as is fully described in Rowland United States Letters Patent No. 3,684,348 granted Aug. 15, 1972. In an effort to accommodate the problems of utilizing such retroreflective materials in roadways, Applicant has proposed a cannister assembly having a prism element for directing the light onto the surface of a retroreflective element sealed within the body of the cannister as is fully described in Applicant's copending United States Application Ser. No. 358,174 filed May 7, 1973. Obviously such cannister assemblies require greater installation time and expense than would flexible sheet material which could adhere either upon the surface or within shallow grooves formed in the surface of the roadway.
It is an object of the present invention to provide a novel retroreflective assembly which is capable of retroreflecting light rays impinging thereon at an angle of 10.degree. or less.
It is also an object to provide such a retroreflective assembly which is relatively resistant to abrasion and which is substantially self-cleaning.
Another object is to provide such a retroreflective assembly which may be produced relatively easy and relatively economically substantially entirely from synthetic resins.
Still another object is to provide a novel method for producing a highly effective retroreflective assembly for use in roadways and the like, which method is relatively simple and relatively economical.